Method of forming puncture preventing layer for tire and apparatus employed therefor

ABSTRACT

A method of forming a puncture preventing layer on an inner surface of a pneumatic tire including the steps of extruding sealing material and pulverizing the extruded sealing material into fine particles for coating the inner surface with a layer of the sealing material under pressure through action of centrifugal force. For effecting the above described method in an efficient manner, there is also provided a puncture preventing layer forming apparatus which includes arrangements for holding the tire, extruding the sealing material, and pulverizing the extruded sealing material so as to be coated onto the inner surface of the tire through the action of centrifugal force.

This is a division of application Ser. No. 865,133 filed Dec. 28, 1977.

BACKGROUND OF THE INVENTION

The present invention relates to pneumatic tires and more particularly,to a method of forming puncture preventing layer on an inner surface ofa pneumatic tire and an apparatus employed therefor.

For forming a puncture preventing layer on an inner surface of apneumatic tire, there has been known a method in which such a layer isformed by a sealing material during molding or after molding of a greenor unfinished tire, in which case, however, the green tire is furthersubjected to vulvanization process, and since such sealing material, ifcomparatively small in viscosity, tends to become uneven in qualityduring the vulcanization, it is very difficult to obtain the punctureprevention layer of a predetermined quality. Therefore, depending on thekinds of the sealing materials, such puncture prevention layer shouldpreferably be formed after vulcanization of the green tire. In thiscase, there may be employed one method in which a sealing materialextruded into a sheet-like form is applied onto the inner surface of thetire, and another method in which the sealing material is sprayed ontothe inner surface of the tire to form thereon the puncture preventionlayer. Although the latter spraying method is preferable due to itssimplicity, there are such disadvantages that, in the known highpressure (high temperature) spraying, the sealing material must be in astate close to liquid, and if powder rubber or the like is contained inthe sealing material, clogging may result during the spraying, thus thesealing material which can be employed being undesirably limited.

Accordingly, an essential object of the present invention is to providean improved method of forming puncture preventing layer for a pneumatictire in which a sealing material extruded even of high viscosity ispulverized into fine particles for being coated under pressure onto aninner surface of a pneumatic tire through centrifugal force, withoutpossibility of clogging during spraying.

Another important object of the present invention is to provide anapparatus which is employable for effecting the puncture preventinglayer forming method as described above in an efficient manner.

A further object of the present invention is to provide an apparatus ofthe above described type which is simple in construction and accurate infunctioning, and can be manufactured at low cost.

SUMMARY OF THE INVENTION

In accomplishing these and other objects, according to the presentinvention, the method of forming a puncture preventing layer on an innersurface of a pneumatic tire includes the steps of extruding sealingmaterial, and pulverizing the extruded sealing material into fineparticles for coating the inner surface of the tire with such sealingmaterial under pressure through action of centrifugal force to form thepuncture preventing layer on the inner surface of the tire.

For effecting the above described method in an efficient manner, thereis also provided a puncture preventing layer forming apparatus whichincludes means for holding the tire, means for extruding sealingmaterial, and means for pulverizing the extruded sealing material so asto be coated under pressure onto the inner surface of the tire throughaction of centrifugal force.

By the above arrangement, it has been made possible to pulverize even asealing material of high viscosity for efficient spraying of suchsealing material onto the inner surface of the tire to form the puncturepreventing layer thereon without possibility of clogging during sprayingeven when powder rubber or the like happens to be contained in thesealing material, with substantial elimination of disadvantages inherentin the conventional puncture preventing layer forming methods andapparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome apparent from the following description taken in conjunction withthe preferred embodiment thereof with reference to the accompanyingdrawings, in which;

FIG. 1 is a sectional view of a pneumatic tire, with an inner tuberemoved away, in which a puncture preventing layer is formed accordingto the puncture preventing layer forming method and apparatus thereforof the present invention, and

FIG. 2 is a schematic side elevational view, partly in section, showingconstruction of the puncture preventing layer forming apparatus of thepresent invention.

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the pneumatic tire or tire cover 1 to which thepresent invention may be applied includes a tread portion 1a, a pair ofopposed side wall portions 1d contiguous to both sides of the treadportion 1a, a pair of bead portions 1b in which bead cores 1c arerespectively embedded, and a carcass portion 1e, for example, of abias-ply defining the inner surface of the tire 1 in a known manner. Thetire 1 further includes a puncture preventing layer P formed accordingto the method and apparatus of the present invention on the innersurface 1e in a position generally corresponding to the tread portion 1aas shown.

Referring also to FIG. 2, there is shown an apparatus T of the presentinvention for forming the puncture preventing layer P of FIG. 1 whichgenerally comprises means for holding the tire 1, means for extrudingsealing material 4 and means for pulverizing the extruded sealingmaterial for application thereof onto the inner surface 1e of the tire 1under pressure to form the puncture preventing layer P on said innersurface 1e. More specifically, the apparatus T includes a base portion16 of rectangular box-like configuration for a shifting device 12 whichis movably disposed at a lower portion of the apparatus T and on which apair of spaced columns 16a extend upwardly from the upper surface of thebase portion 16 for rotatably supporting therebetween a driving roller 2having a concave face and associated, through a suitable transmissionmeans, for example, a chain and sprocket mechanism and the like, with afirst motor 14 placed on the base portion 16, and an upper frame 16b ofgenerally rectangular shape which also extends upwardly from the surfaceof the base portion 16 over the spaced columns 16a. From the tophorizontal portion 16b-1 of the rectangular frame 16b, two spacedsupports 16b-2 corresponding in positions to the support columns 16extend downwardly to support therebetween a guide roller 2' having acorresponding concave face through sliding members 16b-3 slidably fittedover the lower end of the supports 16b-2 to be retained thereat andnormally urged downward, for example, by spring means S disposed aroundthe supports 16b-2, so that when a pneumatic tire 1 is disposed betweenthe rollers 2 and 2', such a tire is depressed toward the driving roller2 by the guide roller 2' and held between the rollers 2 and 2' in aknown manner. In positions adjacent to the bead portions 1b (FIG. 1) ofthe tire 1, there are disposed cylinders 3 each having a rotaryexpanding wheel 15 at its forward end for expanding the bead portions 1bof the tire 1 outwardly and secured to corresponding brackets extendinginwardly from the upper frame 16 as shown.

It should be noted here that each of the cylinders 3 is coupled to asource 100 of working medium or power fluid through a suitable controldevice 101 as shown by chain lines in FIG. 2.

The base portion 16 of the shifting device 12 further includes aplurality of wheels 17 provided for displacement of the base portion 16on the lower surface thereof, which wheels 17 are rotatable on a guiderail 20 disposed on the ground level, and a screw bar 19 horizontallyextending in said base portion 16 and threadedly engaged with acorresponding threaded member 19a which is rotatably supported on asupport or stopper 19b secured to the guide rail 20 to be associatedwith a second motor 18, for example, through a chain and sprocketmechanism.

Accordingly, upon rotation of the second motor 18, the base portion 16is movable together with the drive roller 2, guide roller 2', andcylinders 3 supported on the spaced columns 16a and rectangular frame16b in directions indicated by the arrow a, i.e., in the axial directionof the tire 1 held between the rollers 2 and 2'.

The apparatus T further comprises a sealing material spraying device 21fixedly disposed, for example, at the right of the axis of the tire 1 onan L-shaped frame F extending upwardly from the ground. The sealingmaterial supplying device 21 includes a cylinder 6 enclosed in a heatingdevice 13 and a piston 5 housed in the cylinder 6 and coupled with theworking medium source 100 through the control device 101 forreciprocation within the cylinder 6 so as to extrude the sealingmaterial 4 contained in the cylinder 6 through a bore 7 of smalldiameter which is formed in the forward portion of said cylinder 6 andopen at a fixed disc 10 provided on the distal end of the cylinder 6.

In a corresponding position facing the fixed disc 10 at the left side ofthe axis of the tire 1, there is provided a rotary disc 9 in a coaxialrelation to the fixed disc 10, with the rotary disc 9 being coupled, forhigh speed rotation thereof in a direction shown by an arrow, with ashaft of a third motor 22 which is secured adjacent to one end of asupport shaft 11. The other end of the supported shaft 11 is threadedfor engagement with one end of a screw bar 24 rotatably mounted on anupper horizontal arm Fa of the frame F, while the other end of the screwbar 24 is associated for rotation with a fourth motor 23, for example,by a chain and sprocket mechanism and the like. Since the support shaft11 is prevented from rotation by a guide member or stopper 11a secured,at its one end, to a corresponding end of the horizontal arm Fa of theframe F, said support shaft 11 together with the motor 22, and rotarydisc 9 can be selectively moved in the directions indicated by arrows bupon rotation of the screw bar 24 in the direction shown by the motor23, by which arrangement, it is possible to set the tire 1 between therollers 2 and 2' or remove the same tire 1 held between the said rollers2 and 2', while simultaneously, the rotary disc 9 can be held inposition with respect to the fixed disc 10, with a small clearance 8provided therebetween for spraying the sealing material 4 therethroughonto the inner surface 1e of the tire 1.

With the employment of the apparatus T as described in the foregoing,the method of forming the puncture preventing layer P in the innersurface 1e of the tire 1 will be described step by step hereinbelow.

(1) After the rotary disc 9 has been retracted to the left in FIG. 2,the tire 1 is mounted on the driving roller 2 for being held in positionbetween the guide roller 2' and driving roller 2.

(2) The bead portions 1b of the tire 1 are expanded toward the left andright sides of the tire axis up to predetermined positions by thecylinders 3 having the expanding wheels 15.

(3) The rotary disc 9 is brought toward the fixed disc 10 up to such aposition that there is provided the predetermined clearance 8therebetween.

(4) The tire 1 held between the rollers 2 and 2' is rotated at a lowspeed by driving the driving roller 2.

(5) By operating the piston 5, the sealing material 4 accommodated inthe cylinder 6 is extruded through the bore 7 and the clearance 8.

(6) Simultaneously with or before or after the procedure in the aboveitem 5, the rotary disc 9 is rotated at a high speed for spraying thesealing material 4 through centrifugal force.

(7) Meanwhile, the tire 1 held between the rollers 2 and 2' is moved ata low speed from the left to the right or from the right to the left inFIG. 2 along the axis of the tire 1 so that the sealing material 4 issprayed only onto the predetermined portion of the inner surface 1e ofthe tire 1.

(8) Upon completion of the spraying, the rotary disc 9 is spaced awayfrom the fixed disc 10, and the tire 1 held between the rollers 2 and 2'is removed.

It should be noted here that the method of forming puncture preventinglayer according to the present invention is not limited, in itsapplication, to the foregoing procedures, but may be altered in itsorder within the scope depending on the necessity.

It should also be noted that in the apparatus T according to the presentinvention, the fixed disc 10 and the rotary disc 9 may be modified to bechanged in their positions with each other, or to be rotated indirections opposite to each other. In any case, in the presentinvention, these two discs 9 and 10 form means for pulverizing thesealing material and applying the same under pressure onto the innersurface of the tire through centrifugal force.

It is further to be noted that the angle and the like of the clearance 8formed between the two discs 9 and 10 may be suitably selected toprovide the optimum condition for the spraying.

Given below is one Example carried out through the method as describedin the foregoing with the employment of the apparatus T according to thepresent invention.

EXAMPLE

    ______________________________________                                        Working conditions                                                            ______________________________________                                        (i) Composition of the sealing material                                       Polybutene     100                                                            Polyisobutylene                                                                              20                                                             Aerogel        20                                                             Powder rubber  30                                                             (ii) Temperature of sealing material                                                                   150° C.                                       (iii) Distance of the clearace 8                                                                       1.5mm                                                (iv) Revolutions of the rotary disc 9                                                                  4,500r.p.m.                                          ______________________________________                                    

Results

The puncture preventing layer of the predetermined thickness could beformed.

According to the method of the present invention as described in theforegoing, it is possible to pulverize even a high viscosity sealingmaterial (for example, having 100,000 cps at a temperature of 150° C.)which was considered impossible to be formed into spray up to thepresent for application onto the inner surfaces of tires under pressurethrough action of centrifugal force. It is another advantage of themethod and apparatus according to the present invention that even asealing material containing therein powder rubber and the like can becoated under pressure onto the inner surfaces of tires without causinginconveniences such as clogging during spraying inherent in theconventional methods and arrangements.

Although the present invention has been fully described by way ofexample with reference to the attached drawings, it is to be noted thatvarious changes and modifications are apparent to those skilled in theart. Therefore, unless otherwise such changes and modifications departfrom the scope of the present invention, they should be construed asincluded therein.

What is claimed is:
 1. An apparatus for coating the inner surface of atire casing with a puncture sealing material having a high viscosity,said apparatus comprisingmeans for extruding a stream of said puncturesealing material, means disposed to intercept and break up the resultingstream into a spray comprising a first disc having an openingtherethrough for passage of said stream and disposed across the streamwith the opening aligned therewith, and a second disc disposed acrossthe stream spaced downstream of and facing the first disc, said seconddisc having a flat surface which intercepts the stream, means forrotating the disc having said flat surface whereby the stream impingingthereon is propelled radially outwardly from the space between the discsas a spray, means for supporting and rotating a tire casing having anannular inner open side with the open side disposed to receive the saidspray, said supporting and rotating means comprising a pair of spacedrollers disposed to press against the radial outer surface of the tirecasing diametrically opposite each other, means for biasing a first ofsaid pair of rollers against the tire casing, means for rotating thesecond of said pair of rollers to rotate the tire casing, means formoving the said rollers relative to the said spray for interceptionthereof, and means for spreading the open side of the casing comprisinga pressure cylinder having a reciprocating piston therein, said pistonfixed to a piston rod which extends externally of the pressure cylinderand having a rotary disc fixed to its exposed end and disposed on eachside of the tire casing adjacent said open side for spreading the casingapart to enlarge the opening for reception of the spray, and means forsupplying a fluid under pressure to the pressure cylinder for actuatingthe piston.
 2. An apparatus as claimed in claim 1, wherein said sealingmaterial extruding means is provided with a cylinder equipped with aheating device and having opening of small diameter at a forward endportion of said cylinder, and a piston reciprocatingly accommodated insaid cylinder.
 3. An apparatus as claimed in claim 1, wherein said meansfor pulverizing the extruded sealing material has a first disc providedat the forward end of said cylinder, and a second disc disposed in acoaxial relation to said first disc with a predetermined clearanceprovided therebetween, said first and second discs being adapted to berelatively rotated at high speed.